Info
ER (oestrogen receptor)
A molecular marker that shows whether the tumor responds to the oestrogen in the body. ER positive opens the way to hormone therapy.
What it means
A protein present in some tumor cells that responds to the oestrogen in the body. ER positive tumors can be stimulated by oestrogen — but they can also respond to hormone therapy.
In short
A molecular marker that shows whether the tumor responds to the oestrogen in the body. ER positive opens the way to hormone therapy.
Where you will see it
Mentioned in the immunohistochemistry (IHC) report, usually together with PR, HER2 and Ki-67. Frequently tested in breast cancer.
What it does not tell you on its own
ER positive does not automatically mean that hormone therapy is enough — the decision includes the stage, the grade, HER2 and Ki-67.
Questions for your doctor
- Am I ER positive or negative?
- What percentage of the cells are ER positive?
- Does this mean I can have hormone therapy?
- Is hormone therapy enough or do I also need chemotherapy?
Related terms
The terms below often appear alongside this one. Each definition is right here, so you do not have to look elsewhere.
- Immunohistochemistry
- A laboratory technique that uses antibodies to detect specific proteins in tumor cells. It helps establish the exact type of cancer and choose the right treatment, especially in breast, colon and lung cancers.
- PR (progesterone receptor)
- A protein present in some tumor cells that responds to the hormone progesterone. It is tested together with ER, HER2 and Ki-67 to characterise the molecular type of the tumor.
- HER2
- A protein that can be present in large amounts on the surface of some cancer cells. HER2 positive means that the tumor may respond to specific biological treatments that target this protein.
- Hormone therapy
- A treatment that blocks or reduces the effect of certain hormones that can drive the growth of some tumors, such as some breast or prostate cancers. It is usually given over the long term and is part of the overall cancer treatment plan.
Other terms in “Diagnosis”
Glossary definitions are written for patients by the OncoDots team and go through internal medical review. They explain terms; they do not establish a diagnosis and do not recommend a treatment.